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Faunsdale, AL | If one phase of an ungrounded 480 delta is grounded, then nothing happens, it simply becomes a "corner grounded delta". Actually in some ways it's a better situation than opeating ungrounded. Voltage is stabiized and referenced to ground and phase to phase voltages remain the same. 3 phase equipment operates normally.
Ungrounded services can experience arcing faults which result in overvoltage damage to a lot of equipment all at the same time. I've seen a diagram of how the overvoltage comes about, but don't ask me to explain it! It's only on ungrounded service and with arcing faults. Ungrounded service has an advantage that a fault to ground (a "short") doesn't create a problem, everything operates as before except one phase voltage to ground will become 0. The problem comes when a second phase also has a short to ground! Then current will flow between the two shorts on the two different phases. These systems are usually only used where downtime is really expensive and where there are qualified electricians on staff to chase down any faults before they become a problem. | |
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Which electric power should I use?
